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Artist's impression of a broken asteroid
For most of the threats to mankind — war, famine, disease, environmental meltdown — technology plays second fiddle to wisdom as our best option to avert disaster. But one catastrophe can only be overcome by technology, and lots of it: asteroid impact.
The accepted wisdom is that there have been five extinction-level impacts in the last half-billion years, each one wiping out on average half the species on earth. Unlike the dinosaurs, we have spaceflight: with current technology and enough warning, we could nudge an incoming asteroid out of harm's way. But we have to know it's there, which is where Nasa comes in.
Image credit: Nasa/JPL-Caltech
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